Wireless peripheral interface with universal serial bus port

ABSTRACT

A bus host designed to manage connection and disconnection of devices to and from a wired hub which includes a transceiver for wireless communication with wireless devices. The hub simulates wired connection in response to reception of a wireless signal from the wireless device.

Communication bus systems are systems that provide for shared means forcommunication of data between interconnected devices. Many bus systemsare “open” in the sense that the number of devices connected to the buscan be adapted to the needs of the user more or less arbitrarily. Indynamical bus systems the number of actively connected devices can evenbe changed “on the run”, while the system continues operation. Ofcourse, the bus system has to be specifically designed to support suchdynamical operation, in order that newly activated devices can startparticipating in communication and in order that deactivation of devicesdoes not lead to errors.

The realization of dynamical operation has to account for the type ofcoupling that is used in the communication. Necessarily it is differentin “wired” busses and “wireless” busses.

The IrDA bus is an example of a wireless bus. The IrDA bus is aninfrared bus for communication between devices. An IrDA system containsa host and peripherals both with an infrared transceiver. The host andthe peripherals communicate with the host via infrared signals. In anormal mode (mode 1) the host polls “bound” devices (devices that havean address). By means of polling the host permits different devices tosend data in different time slots. The IrDA bus allows dynamical changesto the configuration of the IrDA system. Periodically the host hails asyet unbound devices, by polling a dummy address. If there are no bounddevices the host enters a sleep mode (mode 0) in which it does not poll.If an active device detects no hailing signals because the host is inthe sleep mode (mode 0) the device sends a wakeup message to the host,which enters the normal mode (mode 1) in response.

The Universal Serial Bus (USB) is an example of a “wired” bus. USBprovides wired communication in a system with a host and a number ofdevices. USB also provides for power supply from the host to thedevices, but only to a limited extent. The host is connected to thedevices in a tree structure with USB wiring as branches and with hubs atthe points where the tree branches out. The USB system is dynamical inthe sense that devices and hubs can be switched on and off or connectedto the system and disconnected from it at any moment. The host iscapable of detecting an active device connected to USB wiring from theresistance connected to the wiring. When the host detects a device, thedevice is “enumerated”: the host records the active connection of thedevice to the USB wiring and communicates with the device to set up alogic connection. If no device is present, or a device is switched off,the host records that the device connected to the wiring is in suspendmode.

The USB host is designed to supply a limited amount of power supplycurrent to the devices via the USB wiring. The average maximum amount ofpower supply current that is available for a device depends on the modeof operation of the device: in the suspend mode the maximum amount ofcurrent is 0.5 mA, but in the active mode the maximum amount of powersupply current is higher. Hubs pass the power supply current from thehost to the devices that are connected to the hub. That is, the maximumamount of supply current flowing to the hub depends on the number ofdevices connected to the hub. In addition the hub is allowed to draw 0.5mA for its own use.

Amongst others, it is an object of the invention to incorporate awireless communication bus, like the IrDA bus, into a wired bus system,like the USB bus.

The invention provides for a data communication bus system comprising

a wired communication bus;

a host designed to manage connection and disconnection of devices to andfrom the wired communication bus, the host being arranged for detectionof a presence of an active device from an electrical connection to thebus made by an active device,

a hub connected to the host via the bus, the hub comprising a firstwireless transceiver;

a wirelessly coupled device with a second wireless transceiver forcommunication with the first transceiver, the hub being arranged tosimulate the electrical connection in response to reception of awireless signal from the wirelessly coupled device. The wiredcommunication bus is for example a USB bus. To the host of this bus itappears as if the devices have normal wired connections to the hub. Thefact that the devices are coupled to the system by wireless connectionto the host is transparent to the host. Only the hub has to be adaptedfor wireless communication. The hub may use any protocol, such as theIrDA protocol or Bluetooth etc. to communicate with the devices.

In principle, the hub may be provided with its own power supply.However, it is desirable to supply power to the hub from the host. Atypical infrared transceiver requires 5 mA of power supply current. TheUSB bus is designed to supply such an amount of a current, but only toactive devices. If no active device is connected to a wired bus, no morethan 0.5 mA should be drawn from the bus. This is insufficient to supplya transceiver with 5 mA.

The system according to the invention has an embodiment wherein powerfor the operation of the wireless communication is drawn from the wiredbus. In order to keep the consumed power supply consistent with thenumber of active devices the transceiver of the hub is operatedintermittently, with a duty cycle that is adapted to the number ofactive devices. In this way, the hub also simulates the powerconsumption of a wired system toward the host. In a particularembodiment, the transceiver is switched on continuously only if at leastone device has been detected and simulated as an active device to thehost.

It should be noted that the current consumed by the hub is adapted sothat its average current consumption does not exceed the allowableaverage power supply current. This does not necessarily mean that thecurrent drawn by the hub is not allowed to exceed the maximum for shortintervals. In the USB system for example, the current may exceed theaverage for short intervals, as long as no excess current is drawn overlonger intervals. Generally, the relevant period for determining theaverage depends on the design of the host. If the host does not allowsufficient current for long enough intervals, it may be desirable tocharge up a capacitor in the hub with a relatively low supply currentfrom the host during a longer period and to operate the transceiver ofthe hub with a relatively high current from the capacitor during ashorter period.

Preferably, a device that wants to become active repeatedly transmitswake-up signals to the hub, with time intervals between transmissionsthat are not consistently equal to the time interval between theintervals in which the transceiver of the hub is powered.

These and other objects and advantageous aspects of the system anddevice according to the invention will be described in more detail usingthe accompanying figures.

FIG. 1 shows a bus system

FIG. 2 illustrates operation of the system as a function of time

FIG. 1 shows a bus system. The system contains a USB host 10, a firstand second hub 12, 14, wired USB devices 13 a–d, and wirelessly coupleddevices16, 17, 18. The host 10 has wired bus connections 11 a,b to thehubs 12, 14. Host 10 contains a controller 100 and a power supplycircuit 102 coupled to the wired bus connections 11 a,b to the hubs 12,14. The first hub 12 is a conventional USB hub and has wired busconnections (e.g. 11 c) to wired USB devices 13 a–d. The second hub 14contains a controller 142, a bus driver 140 and a transceiver 144, allcoupled to the wired bus connection 11 b. The wirelessly coupled devices16, 17 18 contain each a transceiver 160 and a controller 162.

In operation host 10 communicates with devices 13 a–d, 16, 17, 18 viahubs 12, 14. Host 10 also supplies power to the wired bus connections 11a,b from power supply circuit 102. When no devices 13 a–d, 16, 17, 18are active power supply circuit 102 supplies a minimum level of powersupply current (this is the maximum current that may be drawn by devicesin the suspend mode). When controller 100 detects connection of anactive device 13 a–d, 16, 17, 18 it switches power supply circuit 102 toa state with a higher minimum amount of current that power supplycircuit 102 can supply to the bus connection 11 a,b to which the activedevice is coupled.

The part of the communication that occurs between the host 10 and hubs12, 14 is performed using the conventional USB protocol. The part of thecommunication that occurs between the first hub 12 and the devices 13a–d connected to it also uses the conventional USB protocol. However thepart of the communication that occurs between second hub 14 andwirelessly coupled devices 16, 17, 18 deviates from the USB protocol anduses another protocol, such as the IrDA protocol.

A first mode of operation occurs when hub 14 has not detected any activewirelessly coupled devices 16, 17, 18. In this first mode controller 142periodically activates transceiver 144 to attempt to receive wake-upsignals from the wirelessly coupled devices 16, 17, 18.

FIG. 2 illustrates the activation of transceiver 144 as a function oftime “t”. A first trace shows supply current consumption as a functionof time. At periodic intervals the transceiver 144 is activated andconsumes power supply current from host 10 via wired bus connection 11 bfor transmitting a pulse 20, 21 of infrared radiation modulated withinformation (not shown). Any modulation technique may be used; thistechnique is not essential to the invention. A second trace showsinfrared power transmitted by one or more of the wirelessly coupleddevices 16, 17, 18 as a function of time (for part of the time only).When a device 16, 17, 18 wants to start communicating with host 10, thedevice 16, 17, 18 transmits a wake-up pulse 24, 25, 26 modulated withinformation to second hub 14. If the device 16, 17, 18 does not receivea response, it repeats the wake-up pulse 24, 25, 26. This continuesuntil the device receives a response.

In FIG. 2 a first and second pulse 24, 25 of modulated infrared power donot coincide with pulses 20, 21 in which transceiver 144 is activated.The first and second pulse therefore do not lead to a response fromsecond hub 14. A third pulse 26 coincides with a period 22 in which tietransceiver 144 draws power supply current. As a result transceiver 144will detect the wake-up pulse 26. Transceiver 144 reports the wake-uppulse 26 to controller 142. In response controller 142 executes a setupprocedure. In the setup procedure controller 142 commands driver 140 togenerate signals that simulate electrical connection of a device exactlyas if one of the wired devices 13 a–d where connected to the second hub14. As a result, host 10 will raise the power supply current that can bedrawn from the bus connection 11 b to the second hub 14. With thisraised power supply current transceiver 144 can be supplied permanentlyduring an extended period following the start of pulse 22. Accordingly,the first trace of FIG. 2 shows that transceiver 144 may continuouslyuse power supply current for infrared transmission from the start ofthis period (of course, dependent on the required information exchangewith the wireless devices, transceiver 144 may also be switched offagain in this period; FIG. 2 shows only the extreme situation that it ispermanently on).

After the start of the period 22 in which transceiver 144 receives thewake-up signal, controller 142 sets-up communication with the device 16,17, 18 that has sent the wake-up signal. This may be done for exampleusing the IrDA protocol, by causing transceiver 144 to send back ahailing signal to the device 16, 17, 18, by enumerating the device andbinding it to an address. During this communication the device 16, 17,18 may also transmit infrared signals (not shown) other that the pulses24, 25, 26 but this is not shown in FIG. 2 because it is not essentialfor the invention.

Similarly, host 10 will enumerate the device 16, 17, 18 as a USB deviceand assign a USB address to the device. Subsequently, host 10 may send amessage for the device 16, 17, 18 to the second hub, using theconventional USB protocol. Controller 142 of the second hub receivesthis message, but instead of passing it to a conventional USB device,controller 142 translates the message to a message for the wirelessprotocol used for communication with the wirelessly coupled devices 16,17, 18 and commands transceiver 144 to transmit the translated message.Similarly, wirelessly coupled devices 16, 17, 18 can send back wirelessmessages (not shown), which second hub 14 receives, translates into USBmessages and sends back to host 10.

At some time, wirelessly coupled devices 16, 17, 18 may be deactivated.As each device 16, 17, 18 deactivates, controller 142 causes driver 140to simulate disconnection of the device to host 10. When all devices 16,17, 18 have thus been deactivated, power supply unit 102 in host 10 willreduce the available amount of power supply current. Correspondingly,controller 142 of second hub 14 will switch back to the mode in whichthe transceiver 144 is switched on only intermittently after the end 23of the period 22.

Although the invention has been shown for a USB bus and an infraredinterface, it will be understood that it can be applied as well to otherkinds of busses and interfaces.

1. A data communication bus system comprising: a wired communicationbus; a host designed to manage connection and disconnection of devicesto and from the wired communication bus, the host being arranged fordetection of a presence of an active device from an electricalconnection to the bus made by an active device, a hub connected to thehost via the bus, the hub comprising a first wireless transceiver; awirelessly coupled device with a second wireless transceiver forcommunication with the first transceiver, the hub being arranged tosimulate the electrical connection in response to reception of awireless signal from the wirelessly coupled device; wherein the hub isconfigured for switching on the first wireless transceiverintermittently; and wherein the second wireless transceiver repeatedlytransmits pulses for establishing said communication with the firsttransceiver, the first wireless transceiver being activated to simulatethe electrical connection to the host when one of said pulses occurswhen the first wireless transceiver is switched on by the hub.
 2. Thedata communication bus system according to claim 1, wherein the host hasan output for power supply current coupled to the bus, the host beingarranged to supply up to an average maximum current via the output, themaximum current being dependent on a first count of active devices thatthe host detects to be coupled to the output, the output being coupledto a power supply input of the first transceiver via the bus, the hubcomprising a power management circuit arranged for the switching on thefirst transceiver intermittently, with a duty cycle adapted to a secondcount of active devices for which the hub simulates the electricalconnections, so that an average current drawn by the first transceiverdoes not exceed the average maximum supply current corresponding to thesecond count.
 3. The data communication bus system according to claim 2,wherein the hub is arranged to raise the duty cycle up to maximally 100%when it simulates the electrical connection to the host.
 4. The datacommunication system according to claim 2, wherein the host communicateswith the hub according to the USB protocol, the hub communicating withthe wirelessly coupled device according to a wireless bus protocol, thehub translating messages to and from the wirelessly coupled device so asto simulate to the host that the messages come from and go to a USBdevice.
 5. A hub for use in a data communication bus system with a wiredcommunication bus and a host designed to manage connection anddisconnection of devices to and from the wired communication bus, thehost being arranged for detection of a presence of an active device froman electrical connection to the bus made by an active device, the hubcomprising a first wireless transceiver, the hub being arranged tosimulate the electrical connection in response to reception of awireless signal at the first wireless transceiver from a second wirelesstransceiver for establishing communication with the first transceiver,wherein the hub is configured for switching on the first wirelesstransceiver intermittently; and wherein the second wireless transceiverrepeatedly transmits pulses for establishing said communication with thefirst transceiver, the first wireless transceiver being activated tosimulate the electrical connection to the host when one of said pulsesoccurs when the first wireless transceiver is switched on by the hub. 6.The hub according to claim 5, comprising a power management circuitarranged to switch on the first transceiver intermittently, with a dutycycle adapted to a count of active devices for which the hub simulatesthe electrical connections, so that an average current drawn by thetransceiver does not exceed an average maximum supply currentcorresponding to the count.
 7. The hub according to claim 6, arranged toraise the duty cycle up to maximally 100% when it simulates theelectrical connection to the host.
 8. The hub according to claim 6,arranged to communicate with the host according to the USB protocol, thehub communicating with the wirelessly coupled device according to awireless bus protocol, the hub translating messages to and from thewirelessly coupled device so as to simulate to the host that themessages come from and go to a USB device.
 9. A method of communicatingbetween a wired and a wireless communication bus, the method comprisingthe acts of: simulating electrical connection of a wired device inresponse to reception by a first transceiver of a wireless signal from awirelessly coupled device having a second wireless transceiver forestablishing communication with the first transceiver; switching on thefirst wireless transceiver intermittently; repeatedly transmittingpulses by the second wireless transceiver for establishing saidcommunication with the first transceiver; and activating the firstwireless transceiver to simulate the electrical connection when one ofsaid pulses occurs when the first wireless transceiver is switched on.10. The method according to claim 7, comprising: supplying up to anaverage maximum current via the wired bus, the maximum current beingdependent on a first count of active devices detected to be electricallycoupled to the bus; switching on a transceiver for communication betweenthe wired bus and the wireless bus intermittently, with a duty cycleadapted to a second count of active devices for which active electricalconnections are simulated, so that an average current drawn by the firsttransceiver does not exceed the average maximum supply currentcorresponding to the second count.